To treat with antiseptic; to make something free from disease-causing organisms (British spelling).
From 'antiseptic' combined with the verb-forming suffix '-ise' (British English), parallel to the American '-ize'. This converts the adjective into an action verb.
The British and American spellings of this word (-ise vs -ize) reflect a linguistic split that happened after 1776—even our medical vocabulary carries the marks of historical separation.
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